The Planétarium Rio Tinto Alcan focuses part of its research efforts on finding biosignatures on exoplanets. Thanks to the latest scientific technological leaps, we are on the verge of answering one of the biggest questions of all: are we alone in the Universe? To achieve this, astronomy research gives itself access to the right financial means and human resources by bringing together the best researchers and developing the best instruments and telescopes.
The Planétarium Rio Tinto Alcan has opted to collaborate with the Institute for Research on Exoplanets (iREx), a group of more than 50 researchers from four Québec universities (Université de Montréal, McGill University, Université Laval, Bishop’s University). The Planétarium thus brings its expertise:
- in the field of advanced astronomical instrumentation, making it possible to identify rocky exoplanets by contributing to instruments design for the major astronomical observatories in Hawaii and Chile;
- in the field of data analysis and processing thanks to its data visualization center, whose multimedia capabilities and computing power of the two 360o domes, combined with artificial intelligence, will allow the recognition of biosignatures;
- and, finally, in the popularization of science, not only to raise awareness among a large, ever-growing audience, but also to provide training for students, young researchers and facilitators.
The Planétarium hopes to answer this fundamental question and make Montrealers aware of the importance of biodiversity, whether terrestrial or not.
What is an exoplanet?
An exoplanet is a planet that orbits a star other than our own star, the Sun. The existence of exoplanets was confirmed in the mid-1990s. This discovery is credited to the Swiss team of Michel Mayor and Didier Queloz, Nobel Prize winners in physics in 2019. Before the 1990s, there were only nine planets; since then, thanks to multiple discoveries, there are more than 4,000.
How to find them?
Several methods exist for the detection of exoplanets. The Planétarium and iREx research teams focus on 3 of them. Two are indirect, allowing only to detect the effects of exoplanets on the stars around which they orbit, and one is direct, giving access to real images of exoplanets.
The three methods are efficient and make it possible to characterize exoplanetary systems, from their orbit to their atmosphere, including their mass or their dimensions.
The radial velocimetry method
This method, originally suggested by Michel Mayor and Didier Queloz, allows the study of star travel speeds in the presence of a companion. The spectrum of a star, which is its multi-wavelength signature, forms a rainbow dotted with black lines, essential witnesses to the presence of its components. Without the presence of a companion, a star "at rest" will show a fixed spectrum in time through a spectrograph, an instrument able to analyze this light. However, in the presence of a companion (another star, brown dwarf or planet), we will witness the oscillation of this spectrum. We are looking for this sway to identify the presence of an exoplanet.
Two spectrographs, SPIRou and NIRPS, are under construction to study exoplanets. Essentially, this method looks for the mass of exoplanets. The Planétarium Rio Tinto Alcan is participating in the realization of the NIRPS instrument with the iREx team and a group of international collaborators.
The transit method
This method is based on the eclipse principle. When an exoplanet passes in front or behind a star, the star's luminosity varies. This variation gives us access to a wealth of information, including the planet's diameter, and would even allow us to characterize its atmospheres. This method was developed by David Charbonneau in the late 1990s. It was also used by the Kepler Satellite, which allowed the discovery of several thousand planets, and that is taken up by the Transiting Exoplanet Survey Satellite (TESS), its successor, currently operating in space.
Thanks to Canada's participation in the Webb Space Telescope Project, as early as 2021, it will be possible to analyze more deeply the exoplanets' atmospheres in order to look for biosignatures. The iREx and the Mont-Mégantic Observatory (OMM - Observatoire du Mont-Mégantic) are in pole position thanks to their involvement in the design of the NIRISS/FGS instrument, dedicated to the study of distant atmospheres. The Planétarium Rio Tinto Alcan will also be the best location for the dissemination of these amazing results!
Another method for discovering exoplanets consists of photographing them. This method remains very difficult to implement, because exoplanets are very faint compared to the star around which they orbit and very close to it at our observation distance. Consequently, observation techniques will often consist of “hiding” the light of the star, which pollutes the light of the exoplanet, either by coronagraphy (physical mask in the telescope) or by angular differential imaging, developed in 2008 by a Québec team, Marois, Doyon and Lafrenière, which made it possible to have access to the unique image of the HR8799 extrasolar system.
Animation of real photographs showing the movement of planets in the HR8799 extrasolar system, in their orbit, between July 2009 and July 2016. Credits: Video making & motion interpolation: Jason Wang Data analysis: Christian Marois Orbit determination: Quinn Konopacky Data Taking: Bruce Macintosh Bartender, Ben Zuckerman
Very recently, objects with properties very similar to those of giant exoplanets, but which do not orbit a star, have been discovered in the vicinity of the Sun. They are sometimes called "planemos", a contraction which means planetary-mass objects. These planemos are hard to identify because their intrinsic brightness is very low and we need infrared cameras to detect them. Their initial detection is very difficult because we don't even know where to point our telescope, since planemos do not orbit a star. However, once identified, we can study the properties of their atmosphere, their clouds, their velocity in space, and even how fast these planemos spin on themselves. We can study them with a level of detail that is impossible to achieve for exoplanets orbiting a star, since the stars of these exoplanets blind our instruments and it becomes very difficult to directly detect the exoplanet's light.
Young associations of stars
It is still difficult to fully understand the detailed properties of exoplanets and the details of their initial formation. When we study an exoplanet, we often measure its properties in a relative way compared to its host star : for example, we often measure the ratio of the size of the exoplanet to that of the star. We are still limited in our understanding of exoplanets' properties because we need to know the age of their stars in order to establish their properties accurately. However, we have very few tools available to determine the age of stars. The study of star associations allows us to move forward on this front : these associations that typically group a few hundred stars were formed at the same time from a large molecular cloud. We can thus estimate that this whole group of stars have exactly the same age to approximately know the collective age of all these stars. When we then find an exoplanet orbiting one of these stars, we can then deduce the properties of the exoplanet much more precisely. In addition, we sometimes discover such exoplanets around stars so young that the planet is still forming; we then learn a lot more about the mechanisms that allow exoplanets to form.
The exoplanet research team
- Olivier Hernandez, Ph.D., Director, Astrophysicist
- Jonathan Gagné, Ph.D., Scientific Advisor, Planétarium Rio Tinto Alcan
- René Doyon, Ph.D, Director of the OMM, Professor at the Université de Montréal
- Nathalie Ouellette, Ph.D., Astronomer, Institute for Research on Exoplanets (iREx)
- Lison Malo, Ph.D., Astronomer, Mont-Mégantic Observatory (OMM)
- Étienne Artigau, Ph.D., Astronomer, Institute for Research on Exoplanets (iREx)
- Loïc Albert, Ph.D., Astronomer, Institute for Research on Exoplanets (iREx)
- Nicolas Cowan, Ph.D., Professor at McGill University, Institute for Research on Exoplanets (iREx) and McGill Space Institute (MSI)